Method and apparatus for monitoring and controlling peritoneal dialysis therapy

ABSTRACT

Peritoneal dialysis systems, methods, and catheters are provided for performing peritoneal dialysis therapies. Multiple fluid pathways are provided to a patient&#39;s peritoneal cavity for conveying dialysis fluid to and from the patient.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to the treatment of endstage renal disease. More specifically, the present invention relates tomethods and apparatus for monitoring the performance of peritonealdialysis.

[0002] Using dialysis to support a patient whose renal function hasdecreased to the point where the kidneys no longer sufficiently functionis known. Two principal dialysis methods are utilized: hemodialysis; andperitoneal dialysis.

[0003] In hemodialysis, the patient's blood is passed through anartificial kidney dialysis machine. A membrane in the machine acts as anartificial kidney for cleansing the blood. Because it is anextracorporeal treatment that requires special machinery, certaininherent disadvantages exist with hemodialysis.

[0004] To overcome the disadvantages associated with hemodialysis,peritoneal dialysis was developed. Peritoneal dialysis utilizes thepatient's own peritoneum as a semi-permeable membrane. The peritoneum isa membranous lining of the abdominal body cavity. Due to good perfusion,the peritoneum is capable of acting as a natural semi-permeablemembrane.

[0005] Peritoneal dialysis periodically infuses sterile aqueous solutioninto the peritoneal cavity. This solution is called peritoneal dialysissolution, or dialysate. Diffusion and osmosis exchanges take placebetween the solution and the blood stream across the natural bodymembranes. These exchanges remove the waste products that the kidneysnormally excrete. The waste products typically consist of solutes likeurea and creatinine. The kidneys also maintain the levels of othersubstances such as sodium and water which need to be regulated bydialysis. The diffusion of water and solutes across the peritonealmembrane during dialysis is called ultrafiltration.

[0006] In continuous ambulatory peritoneal dialysis, a dialysis solutionis introduced into the peritoneal cavity utilizing a catheter. Anexchange of solutes between the dialysate and the blood is achieved bydiffusion. Further removal is achieved by providing a suitable osmoticgradient from the blood to the dialysate to permit water outflow fromthe blood. This allows a proper acid-base, electrolyte and fluid balanceto be achieved in the body. The dialysis solution is simply drained fromthe body cavity through the catheter.

[0007] Peritoneal dialysis raises a number of concerns including: thedanger of peritonitis; a lower efficiency and therefore increasedduration of dialysis hours compared to hemodialysis; and costs incurredwhen automated equipment is utilized.

[0008] A number of variations on peritoneal dialysis have been explored.One such variation is automated peritoneal dialysis (“APD”). APD uses amachine, called a cycler, to automatically infuse, dwell, and drainperitoneal dialysis solution to and from the patient's peritonealcavity. APD is particularly attractive to a peritoneal dialysis patient,because it can be performed at night while the patient is asleep. Thisfrees the patient from the day-to-day demands of continuous ambulatoryperitoneal dialysis during his/her waking and working hours.

[0009] The APD sequence typically lasts for several hours. It oftenbegins with an initial drain cycle to empty the peritoneal cavity ofspent dialysate. The APD sequence then proceeds through a succession offill, dwell, and drain phases that follow one after the other. Eachfill/dwell/drain sequence is called a cycle. APD can be and is practicedin a number of different ways.

[0010] Current APD systems do not monitor the patient intraperitonealpressure during a therapy session. Current systems simply limit theexternal pressure (or suction) that a pump can apply to the line orlumen that is attached to the patient catheter. If the patient islocated below the system, sometimes referred to as a cycler, a gravityhead will add to the positive fill pressure that the cycler can apply tothe patient catheter. Conversely, if the patient is located above thecycler, the gravity head will decrease from the positive fill pressurethat the cycler can apply to the patient catheter.

[0011] The monitoring of intraperitoneal pressure would be usefulbecause cyclers will sometimes not fully drain a patient between cycles.Specifically, currently-available cyclers are unable to determinewhether a patient absorbed some fluid or whether some fluid is simplynot able to be drained out because of the position of the patient or thecatheter.

[0012] As a result, some currently-available systems utilize a minimumdrain threshold to determine the amount of fluid that should bedelivered to the patient during the next fill. For example, if 85% ofthe fill volume has been drained when the cycler determines that thepatient is “empty”, the next fill volume will be 100%. If only 80% weredrained, the next fill volume would be limited to 95%.

[0013] A negative ultra filtrate (uF) alarm will sound when the patienthas retained more than a predetermined percentage of the fill volume.The predetermined percentage can typically be either 50% or 100% of thefill volume. However, the patient can override this alarm if he/she doesnot feel overfull. The number of times the patients can override the uFalarm during a single therapy may be limited by the software of thecycler. However, the uF alarm typically does not consider the actualultra filtrate that may also accumulate in the peritoneal cavity alongwith the dialysate.

[0014] Currently-available cyclers fill the patient to a specific,preprogrammed volume during each cycle. The doctor prescribes this fillvolume based upon the patient's size, weight and other factors. However,because currently-available cyclers cannot monitor intraperitonealpressure, the doctor cannot take this factor into account whenformulating the prescription. It is also known that intraperitonealpressure (IPP) has an effect on ultrafiltration (UF).

[0015] FIGS. 1-3 provide schematic illustrations of current APD cyclers.None of them attempt to monitor intraperitoneal pressure.

[0016] Referring to FIG. 1, a cycler 10 a is illustrated which includesa dialysate container 11, a patient 12 and a drain container 13 areillustrated schematically. The infusion of dialysate from the container11 into the patient 12 is caused by the gravitational head indicated at14 while the draining of used dialysate from the patient 12 to the draincontainer 13 is caused by the drain head indicated at 15. The cycler 10a includes no sensors for monitoring the pressure inside the peritoneumof the patient 12. A single lumen 16 connects both the dialysatecontainer 11 and drain container 13 to the patient 12. Valves 17, 18operated by the cycler 10 a control the flow of either dialysate fromthe container 11 to the patient 12 or waste material from the patient 12to the drain container 13.

[0017] Turning to FIG. 2, in the cycler 10 b, the drain container 13 anddialysate container 11 are contained within a pressurized chamber 19.The chamber 19 can be pressurized or evacuated to either fill or drainthe patient. Again, the selective operation of valves 17, 18 controlwhether dialysate is being transferred to or from the patient 12. Again,no sensors are provided for detecting or monitoring intraperitonealpressure of the patient 12.

[0018] Turning to FIG. 3, in the system 10 c, a dialysate container 11is connected to a pump 21 which, in turn, connects the dialysatecontainer 11 to a common lumen or catheter 16 which is connected to thepatient. A fluid flow control valve is provided at 23 and is controlledby the cycler 10 c. The drain container 13 is also connected to a pump24 which, in turn, connects the drain container 13 to the lumen 16. Acontrol valve is again provided at 25.

[0019] The drain and fill rates of the cyclers 10 a-10 c illustrated inFIGS. 1-3 are determined by the gravitational head (see FIG. 1) or thesuction or pressure (see FIGS. 2 and 3) applied to the patient line 16.Typically, the cyclers 10 a-10 c fail to optimize either the fill rateor the drain rate because the pressure is either fixed by thegravitational head or the pressure or suction applied by the chamber 10b of FIG. 2 which occurs at the opposing end of the patient line 16.Thus, without measuring the intraperitoneal pressure or having a way toestimate the same, it is difficult to optimize either the drain or fillrate. In the case of the cycler 10 c in FIG. 3, optimizing the drain orfill rate is guesswork due to the lack of any pressure reading at all.

[0020] Accordingly, there is a need for an improved cycler that measurespatient intraperitoneal pressure during a therapy session, includingboth during the drain and the fill as well as the dwell. Further, thereis a need for an improved cycler that measures intraperitoneal pressureand which would use that data to more completely drain a patient betweencycles. Further, there is a need for an improved cycler which wouldaccurately measure intraperitoneal pressure to avoid overfilling apatient. Finally, there is a need for an improved cycler which wouldmonitor intraperitoneal pressure during both the fill and drain cyclesto optimize the speed at which the patient is filled and drained and totherefore increase the dwell portion of a therapy session.

SUMMARY OF THE INVENTION

[0021] The present invention satisfies the aforenoted needs by providinga system for providing peritoneal dialysis to a patient which comprisesa dialysate container connected to the patient with a first pressuresensor connected in-line therebetween, and a drain container connectedto the patient with a second pressure sensor connected in-linetherebetween.

[0022] In an embodiment, the system further comprises a first pumpdisposed in-line between the dialysate container and the first pressuresensor.

[0023] In an embodiment, the dialysate flows from the dialysatecontainer into the patient under a hydrostatic head.

[0024] In an embodiment, a second pump is disposed in-line between thedrain container and the second pressure sensor.

[0025] In an embodiment, the dialysate flows from the patient to thedrain container under a hydrostatic head.

[0026] In an embodiment, the second pressure sensor measures anintraperitoneal pressure of the patient while dialysate flows from thedialysate container to the patient.

[0027] In an embodiment, the first pressure sensor measures anintraperitoneal pressure of the patient while dialysate flows from thepatient to the drain container.

[0028] In an embodiment, the system further comprises a first lumenconnecting the dialysate container to the first sensor and the firstsensor to a catheter, and a second lumen connecting the drain containerto the second sensor and the second sensor to the catheter, the catheterbeing connected to the patient, a flow of dialysate from the patient tothe drain container evacuating dialysate from the first lumen andcausing said dialysate from the first lumen to flow through the secondlumen and to the drain container.

[0029] In an embodiment, the catheter is a dual lumen catheter.

[0030] In an embodiment, the first and second sensors are redundantin-line pressure/vacuum sensors.

[0031] In an embodiment, the present invention provides a method fordialyzing a patient comprising the steps of: placing a catheter in aperitoneum of the patient; providing at least one dialysate container;connecting the dialysate container to the catheter with a first lumenthat includes a first pressure sensor disposed in-line and between thecatheter and the dialysate container; providing at least one draincontainer; connecting the drain container to the catheter with a secondlumen that includes a second pressure sensor disposed in-line andbetween the catheter and the drain container; transferring dialysatefrom the dialysate container to the peritoneum of the patient andmonitoring an intraperitoneal pressure of the patient with the secondpressure sensor; and transferring dialysate from the peritoneum of thepatient to the drain container and monitoring the intraperitonealpressure of the patient with the first pressure sensor.

[0032] In an embodiment, the step of transferring dialysate from thedialysate container to the peritoneum of the patient further comprisespumping dialysate from the dialysate container to the patient with afirst pump disposed in-line between the dialysate container and thefirst pressure sensor.

[0033] In an embodiment, the step of transferring dialysate from theperitoneum of the patient to the drain container further comprisespumping dialysate from the peritoneum of the patient to the draincontainer with a second pump disposed in-line between the draincontainer and the second pressure sensor.

[0034] In an embodiment, the dialysate container is disposed verticallyabove the peritoneum of the patient and the step of transferringdialysate from the dialysate container to the peritoneum of the patientfurther comprises flowing dialysate from the dialysate container to thepatient under a hydrostatic head.

[0035] In an embodiment, the drain container is disposed verticallybelow the peritoneum of the patient and the step of transferringdialysate from the peritoneum of the patient to the drain containerfurther comprises flowing dialysate from the peritoneum of the patientto the drain container under a hydrostatic head.

[0036] Other objects and advantages of the invention will becomeapparent upon reading the following detailed description and appendedclaims, and upon reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

[0037]FIG. 1 illustrates, schematically, a prior art automatedperitoneal dialysis system;

[0038]FIG. 2 illustrates, schematically, a prior art automatedperitoneal dialysis system;

[0039]FIG. 3 illustrates, schematically, a prior art automatedperitoneal dialysis system;

[0040]FIG. 4 illustrates, schematically, an automated peritonealdialysis system made in accordance with the present invention;

[0041]FIG. 5 illustrates, schematically, a second embodiment of anautomated peritoneal dialysis system made in accordance with the presentinvention;

[0042]FIG. 6 illustrates, schematically, a third embodiment of anautomated peritoneal dialysis system made in accordance with the presentinvention;

[0043]FIG. 7 illustrates, schematically, a fourth embodiment of anautomated peritoneal dialysis system made in accordance with the presentinvention;

[0044]FIG. 8 illustrates a pressure sensor made in accordance with thepresent invention;

[0045]FIG. 9 illustrates a fifth embodiment incorporating dual pumpingchambers and pressure sensors made in accordance with the presentinvention;

[0046]FIG. 10 illustrates, schematically, a dual lumen catheter that canbe utilized with the present invention;

[0047]FIG. 11 is a sectional view taken substantially along line 11-11of FIG. 10;

[0048]FIG. 12 illustrates, graphically, the urea concentration in bloodand the urea concentration in a dialysate during a multiple dwelldialysis session;

[0049]FIG. 13 illustrates, graphically, the concentration of urea in apatient's bloodstream versus the concentration of urea in a dialysatesolution for an automated peritoneal dialysis solution practiced inaccordance with the prior art; and

[0050]FIG. 14 illustrates, graphically, the concentration of urea in apatient's bloodstream versus the concentration of urea in a dialysatefor an automated peritoneal dialysis therapy session carried out inaccordance with the present invention.

[0051] It should be understood that the drawings are not necessarily toscale and that the embodiments are sometimes illustrated by graphicsymbols, phantom lines, diagrammatic representations and fragmentaryviews. In certain instances, details which are not necessary for anunderstanding of the present invention or which render other detailsdifficult to perceive may have been omitted. It should be understood, ofcourse, that the invention is not necessarily limited to the particularembodiments illustrated herein.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0052] Turning to FIG. 4, a cycler 30 includes a dialysate container 11connected to a pump 31. The pump 31 is connected to a pressure sensor32. The pump 31 and pressure sensor 32 are disposed in-line in a lumen33 that connects the dialysate container 11 to a catheter 34. Controlvalves are provided at 35, 36. A drain container 13 is also connected toa pump 36 which is connected to a sensor 37. The pump 36 and sensor 37are also connected in-line to a lumen 38 which connects the draincontainer 13 to the catheter 34. Control valves are again provided at41, 42. During the fill, the pump 31 pumps dialysate from the container11 through the lumen 31 and catheter 34 into the peritoneum (not shown)of the patient 12. During this time, the sensor 37 monitors and measuresthe intraperitoneal pressure. A signal is sent to the controller of thecycler 30 shown schematically at 43. A control panel is indicatedgenerally at 44.

[0053] During the drain, the sensor 31 can accurately monitor andmeasure the intraperitoneal pressure of the patient 12. In theembodiment illustrated in FIG. 4, no pumps or control valves aredisposed between the sensor 32 and the patient 12.

[0054] Turning to FIG. 5, a cycler 50 is illustrated which includesreversible pumping chambers 51, 52 with sensors 53, 54 disposed betweenthe reversible pumping chambers 51, 52 and the patient 12 respectively.Control valves 55 and 56 are disposed on another side of the reversiblepumping chamber 51 and the sensor 53 and control valves 57, 58 areprovided on either side of the reversible pumping chamber 52 and sensor54. The sensors 53, 54 actually measure the pressure on the diaphragmsof the reversible pumping chambers 51, 52.

[0055] Turning to FIG. 6, a cycler 60 is illustrated with a chamber 61for accommodating the drain container 13 and a chamber 62 foraccommodating the dialysate container 11. Each chamber 61, 62 isequipped with an integrated valve assembly and pressure sensor shown at63, 64. In the embodiment 60 shown in FIG. 6, the chamber 61 must becapable of being evacuated. Dialysate may flow from the dialysatecontainer 11 by way of gravity or pressure fill. Again, the sensors ofthe valve assembly/sensor combinations 63, 64 monitor theintraperitoneal pressure of the patient 12 as discussed above.

[0056] In the embodiment 70 illustrated in FIG. 7, the dialysatecontainer 11 and drain container 13 are both connected to integratedcontrol valves and pressure sensors 71, 72. Each of the integratedcontrol valves and pressure sensors 71, 72 are connected to lumens 73,74 respectively which are connected to the catheter 75 a by way of aY-connection. The details of all the Y-connections and clamps are notshown but are known to those skilled in the art. Flow from the dialysatecontainer 11 to the patient is carried out under the gravitational headshown at 75 while flow from the patient to the drain container 13 iscarried out under the gravitational head shown at 76.

[0057]FIG. 8 illustrates one in-line pressure sensor 80 that is suitablefor use with the present invention. Redundant load cells 81, 82 areconnected to the flexible pressure sensing membrane 83 by a vacuumconnected by the line 84, 85. A lumen connecting the cycler to thepatient is shown at 86.

[0058]FIG. 9 illustrates a dual-pumping chamber cassette 87 whichincludes an output line 88 which connects the cassette 87 to the patientand an input line 89 connecting the patient to the cassette 87. The line90 connects the cassette 87 to the dialysate container (not shown). Eachpumping chamber 91, 92 are in communication with all three lines 88, 89and 90. Thus, every line can be connected to either pumping chamber 91,92. The pumping chambers 91, 92 are bound on one side by a commondiaphragm shown at 93. Flow is controlled by the use of diaphragm valvesshown at 94, 95, 96 and 97. Pressure sensors are shown at 120, 121, 122,123, 124, 125. However, pressure sensors 123 and 120 are the sensorsused to measure intraperitoneal pressure in accordance with the presentinvention. The remaining sensors 121, 122, 124, 125 are used to monitorthe operation of the pumps 126, 127.

[0059] When the left diaphragm pump 126 is pushing dialysate to thepatient, the sensor 123 can measure the intraperitoneal pressure throughthe line 89. When the left diaphragm pump 126 is draining fluid from thepatient through the line 89, the sensor 120 can measure intraperitonealpressure through the line 88 and while the right pump 27 is pumpingfluid to the drain container (not shown) through the drain line shownschematically at 128. When the right diaphragm pump 127 is being used todrain fluid from the patient, the sensor 120 can measure intraperitonealpressure while the left diaphragm pump 126 is pumping fluid to the draincontainer (not shown) through the drain line shown schematically at 129.

[0060]FIGS. 10 and 11 illustrate a dual-lumen catheter 100 whichincludes separate passageways 101, 102. The employment of a dual lumencatheter 100 as compared to a dual lumen patient line can move the pointat which the pressure is measured to within the peritoneum itself by wayof communication through the separate flowpaths 101, 102. The dual lumencatheter 100 installs like a single lumen catheter, yet will functioneither as a flow through or a standard catheter. Both fluid pathways101, 102 are used to withdraw and deliver fluid during the drain andfill. While one pathway delivers fluid, the other pathway drains. Theend section, shown generally at 103, is perforated.

[0061] A comparison of an APD therapy for a prior art APD cyclers andone manufactured in accordance with the present invention are summarizedas follows: Therapy Parameter Current APD Cycler Cycler Using InventionTotal Therapy Volume 15 liters 15 liters Fill Volume 2.2 liters 2.5liters max Fill Pressure Limit not applicable 14 mm Hg max Total TherapyTime 8 hours 8 hours Last (Day) Fill Volume 1,500 ml 1,500 ml Last FillDextrose Same Same Initial Drain Alarm 1,200 ml 1,200 ml Drain X of NAlarm 80% 80%

[0062] TABLE 1 Comparison of Therapies for Current Cyclers versus Cyclerusing Invention Method Therapy Phase Therapy Parameter Prior Art Cycler1 Prior Art Cycler 2 Invention Cycler 3 Initial Drain Drain Volume 1,200ml 1,200 ml 1,200 ml Patient Volume   300 ml   300 ml   300 ml Fill 1 of5 Fill Volume 2,200 ml 2,200 ml 2,500 ml Patient Volume 2,500 2,5002,800 Fill Pressure not applicable not applicable   12 mm Hg Drain 1 of5 Drain Volume 1,800 ml 2,200 ml 2,200 ml Patient Volume   700 ml   300ml   600 ml Fill 2 of 5 Fill Volume 2,200 ml 2,200 ml 2,400 ml PatientVolume 2,900 ml 2,500 ml 3,000 ml Patient Pressure not applicable notapplicable   14 mm Hg Drain 2 of 5 Drain Volume 1,800 ml 2,200 ml 2,200ml Patient Volume 1,100 ml   300 ml   800 ml Fill 3 of 5 Fill Volume2,200 ml 2,200 ml 2,200 ml Patient Volume 3,300 ml 2,500 ml 3,000 mlPatient Pressure not applicable not applicable   14 mm Hg Drain 3 of 5Drain Volume 1,801 ml 2,200 ml 2,200 ml Patient Volume 1,499 ml   300 ml  800 ml Fill 4 of 5 Fill Volume 2,200 ml 2,200 ml 2,200 ml PatientVolume 3,699 ml 2,500 3.000 ml Patient Pressure not applicable notapplicable 3,000 ml Drain 4 of 5 Drain Volume 1,800 ml 2,200 ml 2,200 mlPatient Volume 1,899 ml   300 ml   800 ml Fill 5 of 5 Fill Volume uFAlarm Bypass 2,200 ml 2,200 ml 2,200 ml Patient Volume 4,099 ml 2,500 ml 3,00 ml Patient Pressure Patient Wakes not applicable   14 mm HgOverfull, Manually Drains 1,500 ml Drain 5 of 5 Drain Volume 1,800 ml2,200 ml 2,200 ml Patient Volume   799 ml   300 ml   800 ml Final FillFill Volume 1,500 ml 1,500 ml 1,500 ml

[0063] Inspection of Table 1 shows that cycler 1 woke the patient ataround 4:30 in the morning with a negative uF alarm at the beginning ofFill 5. The patient bypassed the alarm because he did not feel overfulland immediately fell back asleep. He woke up about 15 minutes later whenhe had difficulty breathing and felt extremely overfull. He manuallydrained about 1500 ml but was unable to go back to sleep. He filed aformal product complaint with the manufacturer.

[0064] The data of Table 1 shows that cycler 2 ran a completely normaltherapy but the total therapy clearance (calculated based upon the sumof the night patient volumes) was only 84.5% of that obtained by cycler3, which was using the cycler that used the method of the currentinvention.

[0065] The data of Table 1 shows that cycler 3 ran a completely normaltherapy and that the fill volume was limited on one occasion by themaximum fill volume but on four occasions by the patient'sintraperitoneal pressure. This patient never felt any discomfort and hadno alarms during the night. The limit on the IPP prevented him frombeing overfilled even though he had successive drains that were notcomplete. The volume of fluid in his peritoneum never exceeded 3 liters.

[0066] The patient on cycler 1 had an intraperitoneal pressure in excessof 14 mm Hg during dwells 3 and 4. His breathing may have been impairedand his heart may have had to work harder but the discomfort was notenough to wake him up from a sound sleep until it peaked at 4,099 mlduring dwell 5.

[0067] In conclusion, the method of the present invention provides foroptimum fills and therefore more clearance while preventing overfillsthat bring discomfort and inhibit the function of vital body organs. Anegative uF alarm would seldom occur because overfills of the requiredmagnitude would be prevented by the IPP sensors.

CALCULATION OF INTRAPERITONEAL PRESSURE (IPP)

[0068] In order to calculate the IPP, one may first calculate thepatient head height correction using conservation of energy:

Δ(1/2ρV ² +P−ρa _(g) h)+Frictional Losses=0

[0069] The velocity V of fluid through the patient line is the same atboth ends of the line as is the fluid density, so this equation can bewritten as

(P ₂ −P ₁)−ρa _(g)(h ₂ −h ₁)+Frictional Losses=0

[0070] which can be rearranged as${\Delta \quad h} = \frac{\left( {P_{1}–\quad P_{2}} \right) - {{Frictional}\quad {Losses}}}{\rho \quad a_{g}}$

EXAMPLE 1

[0071] P1=1.25 psig=85060 (gram/cm)/(cm²-sec²)

[0072] P2=0.9 psig=61240 (gram/cm)/(cm²-sec²)

[0073] Frictional Losses=39130 (gram/cm)/(cm²-sec²) with flow of 197cmn/min in a 4 mm ID line at a velocity of approximately 172 cm/sec,wherein

[0074] a_(g)=981 cm/sec²

[0075] ρ=1 gram/cm³${\Delta \quad h} = \frac{\left( {\left( {85060 - 61240} \right) - 39130} \right){\left( {{gram}/{cm}} \right)/\left( {{cm}^{2} - \sec^{2}} \right)}}{1\quad {{gram}/{cm}^{3}}*981\quad {{cm}/\sec^{2}}}$

[0076] Δh=−15.6 cm (The patient is 15.6 cm below the membrane)

EXAMPLE 2

[0077] P1=1.25 psig=85060 (gram/cm)/(cm²-sec²)

[0078] P2=0.45 psig=30620 (gram/cm)/(cm²-sec²)

[0079] Frictional Losses=39130 (gram/cm)/(cm²-sec²) with flow of 197cmn/min in a 4 mm ID line at a velocity of approximately 172 cm/sec,wherein

[0080] a_(g)=981 cm/sec²

[0081] ρ=1 gram/cm³${\Delta \quad h} = \frac{\left( {\left( {85060 - 30620} \right) - 39130} \right){\left( {{gram}/{cm}} \right)/\left( {{cm}^{2} - \sec^{2}} \right)}}{1\quad {{gram}/{cm}^{3}}*981\quad {{cm}/\sec^{2}}}$

[0082] Δh=+15.6 cm (The patient is 15.6 cm above the membrane)

[0083] The patient head height can be established at the beginning ofeach fill. Any changes in the head height that occur during the fill canbe attributed to an increase in intraperitoneal pressure (IPP) since thepatient is asleep.

[0084] Turning to FIG. 12, the concentration gradient between the ureaconcentration 110 in the patient's blood and the urea concentration 111in the dialysate for typical APD cyclers is illustrated graphically.Comparing the results illustrated in FIGS. 13 and 14, it is evident thatAPD cyclers equipped with the sensors of the present invention providesuperior results. Specifically, the data illustrated graphically in FIG.13 was obtained using a prior art APD cycler. The data obtained in FIG.14 was obtained using an APD cycler utilizing two sensors for monitoringintraperitoneal pressure. Note that the urea concentration 110 in thebloodstream is lower in FIG. 14 than in FIG. 13. Further note, thedialysate volume or fill volume is lower for the therapy illustrated inFIG. 14 than the therapy illustrated in FIG. 13. Thus, the presentinvention provides improved urea clearance with lower fill volumes.

[0085] It should be understood that various changes and modifications tothe presently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications may be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is, therefore, intendedthat such changes and modifications be covered by the appended claims.

The invention is claimed as follows:
 1. A peritoneal dialysis catheterdesigned to be implanted into a patient for conveying fluid from a fluidsource to and from the patient, the catheter comprising: a body having afirst end and a second end defining an implantable portion; a firstlumen defining a fluid path from the first end to the implantableportion; and a second lumen defining a fluid path from the first end tothe implantable portion; the first and second lumens each having anopening at the implantable portion allowing fluid to flow from the firstend through each of the fluid paths and out of the implantable portion.2. The peritoneal dialysis catheter of claim 1, wherein the first andsecond lumens allow fluid to flow from each opening at the implantableportion through each of the fluid paths and out of the first end.
 3. Theperitoneal dialysis catheter of claim 1, wherein the first and secondlumens further allow fluid to flow through one fluid path in a firstdirection while also allowing fluid t o flow through the other fluidpath in an opposite direction.
 4. The peritoneal dialysis catheter ofclaim 1, wherein the catheter further comprises a single tube having thefirst and second lumens.
 5. The peritoneal dialysis catheter of claim 1,wherein the first lumen is in a side-by-side arrangement relative to thesecond lumen.
 6. A peritoneal dialysis catheter implantable in aperitoneal cavity of a patient, comprising: a tube having first andsecond lumens, the tube extending from a first end to an implantableportion having a single free end; a fluid opening to the first lumenlocated between the first end and the single free end; and a fluidopening to the second lumen located at the single free end, the singlefree end having a non-linear shape.
 7. The peritoneal dialysis catheterof claim 6, wherein the tube is so positioned and arranged when in usein the peritoneal cavity that fluid flows through both the first andsecond lumens during patient fill.
 8. The peritoneal dialysis catheterof claim 6, wherein the tube is so positioned and arranged when in usein the peritoneal cavity that fluid flows through both the first andsecond lumens during patient drain.
 9. The peritoneal dialysis catheterof claim 7, wherein the tube is so positioned and arranged when in usein the peritoneal cavity that fluid flows through both the first andsecond lumens during patient drain.
 10. The peritoneal dialysis catheterof claim 6, wherein the tube is so positioned and arranged when in usein the peritoneal cavity that one of the first and second lumensdelivers fluid to the patient and another one of the first and secondlumens drains fluid from the patient.
 11. The peritoneal dialysiscatheter of claim 6, wherein the tube is a single tube having the firstand second lumens.
 12. The peritoneal dialysis catheter of claim 6,wherein the single free end has a coiled shape.
 13. A peritonealdialysis system for providing peritoneal dialysis therapy to a patienthaving an implanted peritoneal catheter which has first and secondlumens, the peritoneal dialysis system comprising: a first fluid pathwayin fluid communication with the first lumen of the catheter; a secondfluid pathway in fluid communication with the second lumen of thecatheter; and a fluid conveying mechanism in fluid communication withthe first and second fluid pathways, the fluid conveying mechanism in afill mode delivering fluid through the first fluid pathway to the firstlumen of the catheter and through the second fluid pathway to the secondlumen of the catheter.
 14. The peritoneal dialysis system of claim 13,wherein the fluid conveying mechanism in a drain mode drains fluid fromthe first lumen of the catheter through the first fluid pathway and fromthe second lumen of the catheter through the second fluid pathway. 15.The peritoneal dialysis system of claim 13, wherein the fluid conveyingmechanism in another mode delivers fluid through the first fluid pathwayto the first lumen of the catheter while draining fluid from the secondlumen of the catheter through the second fluid pathway.
 16. Theperitoneal dialysis system of claim 13, wherein the fluid conveyingmechanism further comprises at least one fluid pump and at least onefluid valve fluidly connected to at least one of the first and secondfluid pathways.
 17. A peritoneal dialysis system for providingperitoneal dialysis therapy to a patient having an implanted peritonealcatheter which has first and second lumens, the peritoneal dialysissystem comprising: a first fluid pathway in fluid communication with thefirst lumen of the catheter; a second fluid pathway in fluidcommunication with the second lumen of the catheter; and a fluidconveying mechanism in fluid communication with the first and secondfluid pathways, the fluid conveying mechanism in a drain mode drainsfluid from the first lumen of the catheter through the first fluidpathway and from the second lumen of the catheter through the secondfluid pathway.
 18. The peritoneal dialysis system of claim 17, whereinthe fluid conveying mechanism in another mode delivers fluid through thefirst fluid pathway to the first lumen of the catheter while drainingfrom the second lumen of the catheter through the second fluid pathway.19. A peritoneal dialysis system for providing peritoneal dialysistherapy to a patient, comprising: a dialysate conveying system capableof conveying dialysis fluid to and from the patient; and a catheterfluidly connected to the dialysate conveying system and having first andsecond lumens, the first lumen in a side-by-side arrangement relative tothe second lumen; the catheter so positioned and arranged when in usethat the catheter delivers the dialysis fluid to the patient at a firstcatheter portion and withdraws the dialysis fluid from the patient atsecond catheter portion which is longitudinally spaced from the firstcatheter portion.
 20. The peritoneal dialysis system of claim 19,wherein the dialysate conveying system is an automated peritonealdialysis system.
 21. The peritoneal dialysis system of claim 19, whereinthe catheter is a dual lumen catheter.
 22. The peritoneal dialysissystem of claim 19, wherein the catheter comprises a single tube havingthe first and second lumens.
 23. The peritoneal dialysis system of claim19, wherein the dialysate conveying system conveys the dialysis fluidthrough both the first and second lumens during patient fill.
 24. Theperitoneal dialysis system of claim 19, wherein the dialysate conveyingsystem conveys the dialysis fluid through both the first and secondlumens during patient drain.
 25. The peritoneal dialysis system of claim23, wherein the dialysate conveying system conveys the dialysis fluidthrough both the first and second lumens during patient drain.
 26. Theperitoneal dialysis system of claim 19, wherein the dialysate conveyingsystem delivers fluid to the patient through one of the first and secondlumens and drains fluid from the patient through another one of thefirst and second lumens.
 27. A method of performing peritoneal dialysis,comprising the steps of: conveying dialysis fluid to a peritoneal cavitythrough first and second lumens of a catheter during a patient fillphase; and conveying dialysis fluid away from the peritoneal cavitythrough the first and second lumens of the catheter during a patientdrain phase.
 28. The method of performing peritoneal dialysis of claim27, further comprising the step of conveying fluid to the peritonealcavity through the first lumen and away from the peritoneal cavitythrough the second lumen during another phase of the peritonealdialysis.
 29. The method of performing peritoneal dialysis of claim 27,wherein at least one of the steps of conveying dialysis fluid to theperitoneal cavity and conveying dialysis fluid away from the peritonealcavity further comprises pumping the dialysis fluid.
 30. A method ofperforming peritoneal dialysis, comprising the steps of: providing asource of dialysis fluid; establishing a flow path from the source ofdialysis fluid to a first lumen of a peritoneal dialysis catheter;establishing a flow path from the source of dialysis fluid to a secondlumen of the peritoneal dialysis catheter; and conveying dialysis fluidfrom the source of dialysis fluid through the fluid paths and throughboth of the first and second lumens.
 31. The method of claim 30, furthercomprising the steps of: withdrawing dialysis fluid from both of thefirst and second lumens of the catheter; and conveying the withdrawndialysis fluid to a drain.
 32. The method of claim 30, furthercomprising the step of conveying fluid through the first lumen in apatient fill direction while conveying fluid through the second lumen ina patient drain direction.
 33. The method of claim 31, furthercomprising the step of reversing a direction of flow in at least one ofthe flow paths.
 34. A method of providing peritoneal dialysis to apatient, comprising the steps of: conveying dialysis fluid from adialysis fluid container through a flow path toward the patient; andreversing a direction of dialysis fluid flow in the flow path toward thedialysis fluid container.
 35. The method of claim 34, wherein the stepof reversing a direction of dialysis fluid flow further comprises thestep of operating a fluid control valve in a fluid path connected to thedialysis fluid container.
 36. The method of claim 34, further comprisingthe step of conveying dialysis fluid through first and second lumens ofa catheter to the patient.
 37. The method of claim 34, furthercomprising the step of removing dialysis fluid from the patient throughfirst and second lumens of a catheter.